3.X.C.OrganicCompoundsReading
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Monosaccharide (Simple Carbohydrate) Identification Organic Compound Identification Purpose To recognize that all living things are made of cells and that cells contain carbohydrates, lipids, proteins, and nucleic acids Materials goggles, apron, science journal, Benedict’s solution, materials for a water bath, 13 test tubes, test tube rack, graduated cylinder, pipets, glucose solution, distilled water, apple slice, stirring rods, starch suspension, solution of iodine and potassium iodide, ½ corn kernel, Sudan IV solution, knife or scalpel, peanut seed, cover slip, concave slide, water dropper, compound microscope, I 2 KI solution in bottle with dropper, 1 mL vegetable oil, Biuret reagent Monosaccharides, or simple carbohydrates, can be identified when Benedict’s solution is added and heat is applied. An orange or red precipitate will form when large amounts of glucose are present. If a small amount of glucose is present, then a yellow or green precipitate will form. Read through the following procedure and write what you predict you will observe in each test tube : 1. Start a water bath by placing a 1 L beaker half-filled with water on a hot plate, and bringing water to a boil. 2. Label one test tube "glucose," one test tube "apple," and one tes t tube "water." 3. Add 5 mL of Benedict's solution to each of the three test tubes. 4. Using a c lean pipet, a dd 10 drops of g lucose solution to the "glucose" test tube. 5. Using a clean pipet, add 5 mL of distilled water to a test tube. 6. Place a piece of apple into the tube and crush it with a stirri ng rod. 7. Decant the water into the test tube labeled "apple." 8. Using a clean pipet, add 10 dro ps of distilled water to the "water" test tube. 9. Using a clean stirring rod eac h time, mix the solutions in eac h labeled test tube. 10. Place each of the labeled test tube s in the water bath for approximately two minutes. 11. Remove the test tubes from the water bath and place them in a test tube rack. 12. Record your o bservations in y our science journal. B.1.4, B.1.6 / Curriculum Framework / Why Are Biomolecules Important? Indiana Biology Standards Resource, November 2003 Questions A. What purpose did the “glucose” test tube serve? B. What purpose did the “water” test tube serve? C. Wer e your predictions co rrect? Why? D. Although all organisms c ontain simple carbohydrate s, what other substances could you test and expect a positive identification? ( continued )
Transcript of 3.X.C.OrganicCompoundsReading
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Monosaccharide (Simple Carbohydrate) Identification
Organic Compound Identification
PurposeTo recognize that all
living things are madeof cells and that cellscontain carbohydrates,lipids, proteins, andnucleic acids
Materials
goggles, apron, science journal, Benedict’s
solution, materials for awater bath, 13 testtubes, test tube rack,graduated cylinder,pipets, glucose solution,distilled water, appleslice, stirring rods,starch suspension,solution of iodine andpotassium iodide, ½ cornkernel, Sudan IV
solution, knife orscalpel, peanut seed,cover slip, concave slide,water dropper,compound microscope,I2KI solution in bottlewith dropper, 1 mLvegetable oil, Biuretreagent
Monosaccharides, or simple carbohydrates, can be identified whenBenedict’s solution is added and heat is applied. An orange or redprecipitate will form when large amounts of glucose are present. If asmall amount of glucose is present, then a yellow or green precipitatewill form.Read through the following procedure and write what you predict youwill observe in each test tube:
1. Start a water bath by placing a 1 L beaker half-filled with water ona hot plate, and bringing water to a boil.
2. Label one test tube "glucose," one test tube "apple," and one test
tube "water."3. Add 5 mL of Benedict's solution to each of the three test tubes.4. Using a clean pipet, add 10 drops of glucose solution to
the "glucose" test tube.5. Using a clean pipet, add 5 mL of distilled water to a test tube.6. Place a piece of apple into the tube and crush it with a stirring rod.7. Decant the water into the test tube labeled "apple."8. Using a clean pipet, add 10 drops of distilled water to the
"water" test tube.9. Using a clean stirring rod each time, mix the solutions in each
labeled test tube.
10. Place each of the labeled test tubes in the water bath forapproximately two minutes.11. Remove the test tubes from the water bath and place
them in a test tube rack.12. Record your observations in your science journal.
B.1.4, B.1.6 / Curriculum Framework / Why Are Biomolecules Important?
Indiana Biology Standards Resource, November 2003
Questions
A. What purpose did the “glucose” test tube serve?B. What purpose did the “water” test tube serve?C. Were your predictions correct? Why?
D. Although all organisms contain simple carbohydrates, what othersubstances could you test and expect a positive identification?
(continued )
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Polysaccharide (Starch) Identification
Starches are made up of chains of glucose molecules. Starches can be identified in substances by usinga solution of iodine and potassium iodide (I2KI). A color change from dark blue to black will occur.
1. Label one test tube “starch,” one test tube “potato,” and one test tube “water.”2. Add 5 mL of distilled water to the test tube labeled “starch.”
3. Using a clean pipet, add 5 drops of starch suspension to the test tube.4. Swirl the test tube and then add one drop of I2KI.
5. Add 10 mL of distilled water to the test tube labeled “water.”6. Add one drop of I2KI.
7. Take half of a corn kernel and place a drop of I 2KI on its cut surface.
8. Record your observations in your science journal.
Questions
A. What purpose did the “starch” test tube serve?B. What purpose did the “water” test tube serve?C. Did all of the kernel tissue react with the I2KI? Explain why you think this happened.D. What is the importance of starch in plant cells?
Lipid Identification
Polar compounds are compounds that are positely charged on one side and negatively charged on theother. Lipids are nonpolar substances. Lipids do not dissolve in polar substances such as water, but willdissolve in other nonpolar substances. This particular identification test targets triglycerides, or fatsand oils. Triglycerides can be identified when they react with Sudan IV stain.
1. Label one test tube “oil,” and one test tube “water.”
2. Add 3 drops of Sudan IV solution to each test tube.3. Add 1 mL vegetable oil to the test tube labeled “oil” and 1 mL distilled water to the test tube
labeled “water.”4. Using a clean stirring rod each time, mix the contents of each test tube.5. Record your observations in your science journal.6. Cut a thin slice of a peanut seed and make a wet mount using distilled water.7. Using a compound microscope, observe the tissue under low and high power.8. Remove the slide and place a drop of I2KI on one edge of the cover slip.
(Blot water from the other edge of the cover slip, if needed.)
9. Place the slide back under the microscope and record your observations
in your science journal.10. Add Sudan IV solution to your wet mount.11. Observe the tissue under low and high power.12. Record your observations in your science journal.
(continued )
B.1.4, B.1.6 / Curriculum Framework / Why Are Biomolecules Important?
Indiana Biology Standards Resource, November 2003
Organic Compound Identification (continued)
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B.1.4, B.1.6 / Curriculum Framework / Why Are Biomolecules Important?
Indiana Biology Standards Resource, November 2003
Protein Identification
Proteins consist of sequences of amino acids. There are 20 different amino acids found in livingorganisms. The differences in combinations of amino acids and protein structures allow for thousandsof different proteins to be found in organisms. Proteins consisting of particular amino acids can beidentified when they react with a solution of sodium hydroxide and copper sulfate. A color changeof purple indicates the presence of peptide bonds in the solution. This is called the Biuret test.
1. Choose four substances to test for protein identification, under the following conditions: Onesubstance must be your known positive control and one substance must be your known
negative control.2. Label four test tubes with their corresponding substance identifications.3. For each of the four test tubes, add 1 mL of the corresponding substance.4. Add 1 mL of Biuret reagent to each of the four test tubes.5. Using a clean stirring rod each time, mix the contents of each test tube.6. Record your observations in your science journal.
Questions
A. What substances did you choose as your positive and negative controls? Why?B. What other two substances did you choose to test for presence of proteins? Why?
Questions
A. What purpose did the “oil” test tube serve? What did you observe when Sudan IV was added?B. What purpose did the “water” test tube serve? What did you observe when Sudan IV was added?C. What did the addition of I2KI to the peanut seed show?D. Do you think that Sudan IV is a polar or nonpolar substance? Why?
Organic Compound Identification (continued)
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B.1.4, B.1.6 / Curriculum Framework / Why Are Biomolecules Important?
Indiana Biology Standards Resource, November 2003
Teacher Directions
A. Monosaccharide (Simple Carbohydrate) Identification• To prepare a 10% solution of glucose, add 10 g of glucose in powder
form to a final volume of 100 mL distilled water.• You can purchase Benedict’s solution from any biological supply company.
• Cut apples into small pieces for students to crush in their test tubes.• Aid students as they prepare hot water baths. If more than one lab group is using a hotwater bath, have students label their test tubes with their lab group identifications.
B. Polysaccharide (Starch) Identification• I2KI preparation: Add 1.3 grams iodine to 2 grams of potassium iodide and add to 100 mL
distilled water.• The day before the lab, soak the corn kernals in a bowl of water overnight to
soften them. The day of the lab, cut the corn kernels longitudinally so each groupof students can have one half of a corn kernel.
C. Lipid Identification
• If needed, review with students how to prepare a wet mount.• You can purchase Sudan IV stain from most biological supply companies.• Since Sudan IV is nonpolar, it will move into the lipid droplets of the peanut seed tissue.
D. Protein Identification• You can purchase Biuret reagent from most biological supply companies.• The positive control can be albumin in powder form. To prepare a 10% albumin solution,
add 10 g in a final volume of 100 mL distilled water.
Answer Key
A. Monosaccharide (Simple Carbohydrate) Identificationa. positive controlb. negative controlc. answers will varyd. examples might be table sugar, honey, other fruits
B. Polysaccharide (Starch) Identificationa. positive controlb. negative controlc. No. Only parts of the kernel contain starch.
C. Lipid Identification
a. positive control; Sudan IV dissolved in the oilb. negative control; Sudan IV separated from the waterc. presence of starchd. nonpolar; it did not dissolve in water and did dissolve in oil (like dissolves like)
D. Protein Identificationa. Students should choose a known protein as the positive control and a known nonprotein
(e.g., distilled water) as the negative control.b. Answers will vary.
Organic Compound Identification
